Last reviewed 05/2021
Haptoglobin is an alpha-2-globulin.
The function of haptoglobin is to bind free haemoglobin in the blood, with a capacity of up to 1.4 grams per litre. The haptoglobin-haemoglobin complexes are removed by the reticuloendothelial system, resulting in a reduction in the concentration of haptoglobin.
It is only when the binding capacity is rapidly exceeded - in acute haemolysis - that haemoglobin appears in urine.
Haptoglobin is an acute phase protein, rising in concentration during acute inflammation.